Chemical pathology.

  • Wells, H. Gideon (Harry Gideon), 1875-1943.
Date:
1914
Catalogue details

Licence: In copyright

Credit: Chemical pathology. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    below may be referred to.15 The applications in pathology will be brought out as the subject under discussion in subsequent chapters necessitates, and it is largely to facilitate the understanding of such references that this brief summary of the subject of ionization has been introduced. In the same spirit we take up the subjects of dif- fusion and osmosis. Diffusion and Osmosis.—Although the non-electrolytes do not ion- ize to any considerable extent, and therefore are relatively inactive chemically, the crystalloidal non-electrolytes, of which sugar and urea are the two chief examples among the cell constituents, possess in common with the electrolytes the important property of diffusion. By this process the exchange of chemical substances between the blood and the cell is brought about, by it the chemical composition of the different parts of the cell and between different cells is equalized, and without it chemical change would be practically impossible. Dif- fusion occurs most simply between two solutions of unlike nature, or between a solution of a substance and the solvent alone, when placed directly in contact with one another. If we place in the bot- tom of a cylindrical vessel a solution of copper sulphate and above it some water, carefully avoiding mixing, it will be found after some time that the fluid has become equally blue throughout. This is brought about by the movement of the dissolved particles which gradually carries them through the entire mass of fluid, and as their migration is against the force of gravity, they evidently accomplish work. This process is not dependent upon ionization, for a solution of cane-sugar or of ui’ea will show the same diffusion. A solution of protein or other colloid does so much more slowly, however, indeed quite imperceptibly. If we were to introduce a piece of filter-paper between the water and the copper sulphate solution, the diffusion would go on the same, the pores of the paper permitting the passage of the molecules with- out hindrance. If, instead of filter-paper, there were introduced a sheet of some substance free from pores, the diffusion would be much more affected. If the septum was of such a nature that the sub- stances in solution were insoluble in it (e. g., glass), diffusion would of necessity stop; but if it were something in which the solvent or the solute was soluble, such as a gelatin plate, then these substances would dissolve in it, and diffusing through its substance escape into the fluid on the other side. The last example indicates the conditions 15 “Physical Chemistry in the Service of Medicine,” Wolfgang Pauli, transla- tion by M. II. Fischer, New York, 1907. “Physikalische Chemie der Zelle und der Gewebe,” Hober, Leipzig, 1911. “Osmotische Druck und Ionenlehre in den medicinischen Wissenschaften,” Hamburger, Wiesbaden. “Studies in General Physiology,” Loeb, University of Chicago Press, 1905. “Dynamics of Living Matter,” Loeb, Columbia University Press. New York. 1906. Bottazzi, Ergeb- nisse d. Physiol.. 1908 (7), 161. Spiro and J. Loeb, Oppenheimer’s “Handbuch der Biochemie,” 1908 (2), 1-141.